Can't help on an ID. Sure looks like it could power an ultralight aircraft. Not that there isn't some RC stuff big enough to run that huge of a prop prop but I think you have an early 70’s homebuilt manned ultralight aircraft power plant.
Sachs? Hirth? If you measure the displacement it might help in searching.
Really cool setup!!

Can't help on an ID. Sure looks like it could power an ultralight aircraft. Not that there isn't some RC stuff big enough to run that huge of a prop prop but I think you have an early 70’s homebuilt manned ultralight aircraft power plant.

I looked up some data on prop size vs wingspan and it indicated that a prop this big would be for an airplane with an 80" wingspan, so my guess is one of those REALLY big airplanes, but maybe it could push an ultralight, like one of those powered hang gliders.